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PubMed This is a summary of 9 peer-reviewed journal articles Updated
Cardiology · Pulmonary Arterial Hypertension

Diagnostic Criteria and Ruling Out Look-Alikes

At a Glance

A formal diagnosis of Pulmonary Arterial Hypertension (PAH) requires a Right Heart Catheterization to directly measure lung pressures. This test, along with a V/Q scan, is essential to confirm the diagnosis and safely rule out look-alike conditions that require completely different treatments.

Confirming a diagnosis of Pulmonary Arterial Hypertension (PAH) is a meticulous process. Because the treatments for PAH are powerful and specific, your medical team must prove that your high lung pressure isn’t actually caused by more common conditions like left heart disease or chronic lung disease.

The Gold Standard: Right Heart Catheterization (RHC)

You cannot be formally diagnosed with PAH without a Right Heart Catheterization. While an echocardiogram (an ultrasound of the heart) is a great screening tool, it only provides an estimate of your lung pressure. The RHC involves placing a small tube into your heart to get exact, direct measurements [1].

According to the 2022 ESC/ERS Guidelines, you must meet three specific criteria to be diagnosed with Group 1 PAH [2]. Knowing the “normal” ranges can help you contextualize your own results:

  1. mPAP (Mean Pulmonary Arterial Pressure) > 20 mmHg: (Normal is ~14 mmHg at rest). This confirms that you have pulmonary hypertension (high pressure in the lung’s arteries) [2].
  2. PAWP (Pulmonary Artery Wedge Pressure) ≤ 15 mmHg: (Normal is also ≤ 15). This is a crucial “ruling out” measurement. It proves the pressure isn’t high just because the left side of your heart is struggling to pump [1].
  3. PVR (Pulmonary Vascular Resistance) > 2 Wood Units: (Normal is < 2 Wood Units). This number measures the “friction” or resistance in your vessels. A high PVR means the small arteries in your lungs are physically narrowed or damaged [2].

Ruling Out “Look-Alikes”

It is dangerous to treat everyone with high lung pressure the same way. If a patient with Group 2 (Left Heart Disease) or Group 3 (Lung Disease) is given PAH-specific vasodilators, it can cause fluid to back up into the lungs or lower their oxygen levels significantly [3][4].

A V/Q Scan (Ventilation/Perfusion Scan) is an absolute necessity [5]. It checks for blood clots in the lungs. This is done to rule out CTEPH (Group 4), a condition where old blood clots cause high pressure. CTEPH is often curable with surgery, making it vital to catch [6].

The Vasoreactivity Test

During your RHC, your doctor may perform a vasoreactivity test, often using inhaled nitric oxide. This test is generally only standard and useful for patients with Idiopathic, Heritable, or Drug-induced PAH [7]. It checks if your lung vessels are still capable of relaxing.

  • What is a “Responder”? A person is a “responder” if their lung pressure (mPAP) drops by at least 10 mmHg to reach a total of 40 mmHg or less, without their heart’s output getting worse [8].
  • Why it Matters: Responders are rare (about 10% of IPAH patients) but have a much better outlook [8]. They can often be treated with simple, high-dose calcium channel blockers (blood pressure pills) rather than the more complex and expensive PAH medications [9].

Your Completeness Checklist

Before finalizing a diagnosis of Idiopathic or Heritable PAH, your medical records should ideally contain the following:

  • [ ] Echocardiogram: To look at heart structure and estimate pressures.
  • [ ] Right Heart Catheterization (RHC): To confirm exact pressures (mPAP, PAWP, PVR).
  • [ ] V/Q Scan: To rule out old blood clots (CTEPH).
  • [ ] Pulmonary Function Tests (PFTs): To rule out significant lung disease (Group 3).
  • [ ] High-Resolution CT Scan (HRCT): To look for scarring or other lung issues.
  • [ ] Bloodwork: To check for HIV, liver disease, and connective tissue diseases (like scleroderma).
  • [ ] 6-Minute Walk Test: To measure your current physical capacity.

Common questions in this guide

Why do I need a right heart catheterization if I already had an echocardiogram?
An echocardiogram only provides an estimate of your lung pressures. A right heart catheterization is required for a formal PAH diagnosis because it directly measures the exact pressure and resistance inside your heart and lungs.
What are the diagnostic numbers for a right heart catheterization in PAH?
Under the 2022 guidelines, a PAH diagnosis requires a mean pulmonary arterial pressure (mPAP) greater than 20 mmHg, a pulmonary artery wedge pressure (PAWP) of 15 mmHg or less, and pulmonary vascular resistance (PVR) greater than 2 Wood Units.
Why is a V/Q scan necessary when diagnosing pulmonary hypertension?
A V/Q scan checks for old blood clots in the lungs to rule out a look-alike condition called CTEPH. It is vital to identify CTEPH because, unlike PAH, it can often be cured with surgery.
What is a vasoreactivity test during a heart catheterization?
A vasoreactivity test checks if your lung blood vessels can still relax, usually using inhaled nitric oxide. If your pressures drop significantly, you are considered a responder and may be treated with calcium channel blocker medications.
What happens if PAH medications are used for other types of pulmonary hypertension?
It is dangerous to treat patients who have high lung pressure caused by left heart disease or chronic lung disease with PAH-specific medications. Doing so can cause fluid to back up into the lungs or severely lower oxygen levels.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Does my Right Heart Catheterization report meet all three of the 2022 ESC/ERS criteria (mPAP > 20, PAWP ≤ 15, and PVR > 2)?
  2. 2.Was a V/Q scan performed to rule out CTEPH, or was only a CT scan done? (I've learned a V/Q scan is more sensitive for this).
  3. 3.During my catheterization, was a vasoreactivity test performed? If so, what were the results and does it change my treatment options?
  4. 4.Can you explain how you ruled out Group 2 (left heart disease) and Group 3 (lung disease)? Using PAH drugs for those conditions can be risky, right?
  5. 5.Are there any missing tests from my 'completeness checklist' that we still need to perform?

Questions For You

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References

References (9)
  1. 1

    A review regarding the article `Right heart catheterization in idiopathic pulmonary hypertension: An all-inclusive necessity'.

    Wu J, Jiang Y

    Current problems in cardiology 2024; (49(9)):102673 doi:10.1016/j.cpcardiol.2024.102673.

    PMID: 38782197
  2. 2

    Updated Clinical Classification and Hemodynamic Definitions of Pulmonary Hypertension and Its Clinical Implications.

    Kularatne M, Gerges C, Jevnikar M, et al.

    Journal of cardiovascular development and disease 2024; (11(3)) doi:10.3390/jcdd11030078.

    PMID: 38535101
  3. 3

    Pilot Study of Endothelin Receptor Blockade in Heart Failure with Diastolic Dysfunction and Pulmonary Hypertension (BADDHY-Trial).

    Koller B, Steringer-Mascherbauer R, Ebner CH, et al.

    Heart, lung & circulation 2017; (26(5)):433-441 doi:10.1016/j.hlc.2016.09.004.

    PMID: 27816421
  4. 4

    Impact of targeted pulmonary arterial hypertension therapies in severe pulmonary hypertension in chronic lung diseases.

    Naud R, Bermudez J, Resseguier N, et al.

    ERJ open research 2023; (9(4)) doi:10.1183/23120541.00027-2023.

    PMID: 37609598
  5. 5

    The Role of Lung Ventilation/Perfusion Scan in the Management of Chronic Thromboembolic Pulmonary Hypertension.

    Ha S, Han S

    Nuclear medicine and molecular imaging 2024; (58(7)):449-458 doi:10.1007/s13139-023-00830-5.

    PMID: 39635628
  6. 6

    Diagnosis of chronic thromboembolic pulmonary hypertension.

    Jais X, Tapson V, Fernandes TM, et al.

    The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation 2025; (44(7S)):S1-S7 doi:10.1016/j.healun.2025.02.1688.

    PMID: 40653349
  7. 7

    Prospective safety assessment of the acute vasoreactivity test using an inhaled nitric oxide delivery system in pulmonary hypertension.

    Minatsuki S, Hatano M, Ishii S, et al.

    International journal of cardiology 2026; (444()):134009 doi:10.1016/j.ijcard.2025.134009.

    PMID: 41205827
  8. 8

    Positive Vasoreactivity Testing in Pulmonary Arterial Hypertension: Therapeutic Consequences, Treatment Patterns, and Outcomes in the Modern Management Era.

    Gerhardt F, Fiessler E, Olsson KM, et al.

    Circulation 2024; (149(20)):1549-1564 doi:10.1161/CIRCULATIONAHA.122.063821.

    PMID: 38606558
  9. 9

    Calcium channel blockers in patients with pulmonary arterial hypertension receiving PAH-specific treatment.

    Hirakawa K, Asano R, Ueda J, et al.

    International journal of cardiology 2024; (406()):132043 doi:10.1016/j.ijcard.2024.132043.

    PMID: 38614366

This page provides educational information on the diagnostic criteria for pulmonary arterial hypertension (PAH). It is not a substitute for professional medical advice, and you should always discuss your specific test results with your pulmonologist or cardiologist.

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